A conventional cellular telephone includes a display screen that displays information for use by a user of the telephone. As cellular telephones have evolved to include ever increasing functionality, the display screens of the telephones have correspondingly evolved to provide the capability to display wider ranges of information. As a result, the current generation of digital cellular telephones includes a display screen comprising a liquid crystal display (LCD) capable of displaying both text and images, which display screen is typically illuminated by a backlight for good visibility.
The typical cellular telephone features an automatic display backlight that turns on for a pre-defined period of time after depression of a key in a keypad of the telephone. The time duration of the turn-on period may vary from telephone-to-telephone but typically is approximately 10 seconds. As cellular telephones become more data oriented and include bigger displays capable of displaying more content, the turn-on period may increase in order to enable a user of the telephone to read a full screen of information. In addition, due to such data features as email and Internet browsing, the use of the display backlight may increase in frequency.
The display backlight of a cellular telephone is sourced power by a limited life power source, typically a limited life storage battery. The use of the backlight imposes a current drain on the battery, thereby reducing the remaining life of the battery before the battery requires a recharge. Since the battery provides the power for the operation of all elements of the telephone, battery life is a constraining factor in the operation of a cellular telephone. Battery life is also important marketing feature of cellular telephones as cellular telephone manufacturers distinguish their telephones from other cellular telephones based on, among other things, a number hours of operation of a cellular telephone before the telephone battery must be recharged.
Therefore a need exists for a method and an apparatus in a cellular telephone for optimizing a length of time that a backlight of a cellular telephone is on, thereby preserving a battery life of the battery powering the telephone.